1. Technical Field
The present invention relates to a light guide device used for a head mounted display worn on a head for use or the like and a virtual image display apparatus with the device incorporated therein.
2. Related Art
Recently, as virtual image display apparatuses that enable formation and observation of virtual images such as head mounted displays, various apparatuses that guide image lights from display devices by light guide plates to pupils of observers and enable observation of outside world images through the light guide plates have been proposed.
For example, a projection display apparatus including a first plate-like waveguide having a diffraction grating for output, a second plate-like waveguide having a pair of diffraction gratings for input and output, and an image supply light guide device that supplies image light to one end of the first plate-like waveguide is known (see Patent Document 1 (U.S. Pat. No. 8,965,152)). In the projection display apparatus, the collimated image light enters the first plate-like waveguide from the image supply light guide device and enlarges an exit pupil in horizontal directions within the waveguide, and the output from the first plate-like waveguide enters the second plate-like waveguide and enlarges an exit pupil in vertical directions within the waveguide. Further, in the projection display apparatus, three-layer channels for three colors are provided in the first plate-like waveguide and the second plate-like waveguide, and thereby, color representation can be performed.
According to the technique described in Patent Document 1, there is an advantage that the light guide plate may be made thinner. However, the diffraction gratings, i.e., the diffraction devices are used, and the peak of wavelength selectivity (diffraction efficiency with respect to wavelength) shifts depending on the angle of view of image light and color unevenness depending on the position within the screen is caused.